1. Field of the Invention
The present invention relates to a light source device capable of securing uniformity of in-plane luminance of light emitted from a semiconductor light emitting device array, and a projection type display unit to which the light source device is applied.
2. Description of the Related Art
In recent years, there has been well used a projection type display unit for displaying, in a large screen, a high-precision color image represented by high vision broadcasting standards, ultra extended graphics array (UXGA) standards of computer graphics or the like.
The projection type display unit includes a unit to which a transmission type or reflection type space optical modulation device (e.g., a liquid crystal panel) is applied as an image display device for displaying a color image, a unit to which a digital micromirror device (DMD) is applied, and the like. Furthermore, there are a single plate system in which three colors RGB are displayed in time division, a multi-plate system in which the three colors RGB are separately displayed, and the like in accordance with the number of image display devices for use in the projection type display unit. Various types of structural modes have been applied as the projection type display unit by a combination of them. In recent years, a single-plate DMD has attracted attention, and a projection type display unit to which this DMD is applied has been proposed (e.g., see Japanese Patent Application Laid-Open No. 2000-78602 (pages 3 and 4, FIG. 1)).
Moreover, as a light source device for use in the projection type display unit, there is sometimes used a light emitting diode (LED) array which consumes less power, releases less heat, and has a longer life (e.g., see Japanese Patent No. 3319438 (pages 4 and 5, FIG. 2)).
FIG. 1 is a block diagram showing an image display unit of Prior Art 1.
An image display unit 100 of Prior Art 1 shown in FIG. 1 is described in the Japanese Patent Application Laid-Open No. 2000-78602. The unit will briefly be described with reference to the prior art.
As shown in FIG. 1, in the image display unit 100 of Prior Art 1, a white light emitted from a lamp 101 constituting a light source is separated into a red (R) light, green (G) light, and blue (B) light by a rotatable color wheel 102 which is color extraction means, and the separated color lights are incident upon a digital micromirror device (DMD) 103 to which a large number of micro movable mirrors (not shown) are attached. Here, for the DMD 103, a large number of micro movable mirrors are integrated on one chip, and an inclination of each micro movable mirror is changed with respect to each color light incident upon the chip to selectively control each color light in an ON state in which each color light is incident upon a projection lens side and in an OFF state in which each color light is prevented from being incident upon the projection lens side.
On the other hand, color signals R, G, B are input into a time division multiplex circuit 104, and in the circuit 104 signals G, R, B are time-divided in the same color order as that generated in the color wheel 102 in accordance with a color sequence signal from a color sequence control circuit 105, and then supplied to the DMD 103. In this case, the color wheel 102 includes R, G, B filters every 40° for each of three divided blocks of 120°.
Thereafter, the G, R, B color lights are reflected in a corresponding period by the DMD 103 controlled by the signals G, R, B, and a screen S is irradiated with the output light signals G, R, B in order to display the signals as color images. In this case, the respective color signals are time-divisionally supplied to the DMD 103 as repeated at a high frequency corresponding to a time shorter than a human visual reaction time. Therefore, the respective colors are time-integrated in a human visual sense, and recognized as the color image including white.
The image display unit 100 according to Prior Art 1 has been used in many projection type display units because a constitution of an optical system is simple and the unit is appropriate for miniaturization.
On the other hand, the use of semiconductor light emitting devices such as LED as the light source for the projection type display unit which outputs the color image has been studied.
A light source device 200 of Prior Art 2 shown in FIGS. 2A and 2B is described in the Japanese Patent No. 3319438, and will be briefly described with reference to the drawings.
As shown in FIG. 2A, in the light source device 200 of Prior Art 2, the following arrays are arranged facing three side surfaces of a dichroic prism 201 crossing one another at right angles: a red LED array 203R in which a plurality of red LEDs are two-dimensionally arranged on a substrate 202R for R and a lens array 204R facing the red LED array 203R; a green LED array 203G in which a plurality of green LEDs are two-dimensionally arranged on a substrate 202G for G and a lens array 204G facing the green LED array 203G; and a blue LED array 203B in which a plurality of blue LEDs are two-dimensionally arranged on a substrate 202B for B and a lens array 204B facing the blue LED array 203B.
In this case, as shown in FIG. 2B, for example, for the red LED array 203R, the red LEDs are integrated in a matrix of 5×4 columns, and the respective red LEDs emit the light in the same timing. Moreover, the red light emitted from the red LED array 203R is converted to the light high in parallelism by the lens array 204R, and thereafter incident upon the dichroic prism 201.
Moreover, the red light emitted from the red LED array 203R is reflected by a red reflecting mirror of the dichroic prism 201. Furthermore, the green light emitted from the green LED array 203G is transmitted through the dichroic prism 201. Additionally, the blue light emitted from the blue LED array 203B is reflected by a blue reflecting mirror. In this manner, in the dichroic prism 201, the red, green, and blue lights are synthesized and emitted as a white light from a side surface without the respective color LED arrays 203R, 203G, 203B.
Additionally, when the red LED array 203R, green LED array 203G, and blue LED array 203B used in the light source device 200 of Prior Art 2 are applied to the image display unit 100 of Prior Art 1 instead of the lamp 101, low power consumption, small heat release value, and long life are achieved, but the following new problems occur.
That is, for a first problem, the lens arrays 204R, 204G, 204B for R, G, B are required for the LED arrays 203R, 203G, 203B for the RGB colors, the dichroic prism 201 which is very expensive needs to be used, and it is difficult to reduce costs and sizes of the projection type display unit and the light source device.
Moreover, for a second problem, an emission luminance is not always equal in a plane by emission fluctuations among LEDs in the LED arrays 203R, 203G, 203B for the RGB colors. When the luminance differs with R, G, B, and the white light is displayed, color unevenness appears, and this remarkably degrades an image display quality.